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A potential new tool for fighting HIV infections in women — a microbicide-releasing vaginal ring — reduced infection rates by about a third for African women in two major clinical trials, scientists announced Monday.

This is the first time a vaginal ring has been shown to effectively deliver antiretroviral drugs to women. But the highly anticipated findings, presented at a conference in Boston, were nonetheless met with mixed reactions from researchers and advocates.

While some celebrated the potential arrival of a much-needed prevention tool — researchers are preparing to seek regulatory approval — others were disappointed the vaginal ring fell short of expectations, particularly for women under 21, who received minimal to no protection.

“We would’ve hoped, I think, that the level of protection would actually have been larger than what they observed,” said Dr. Mark Wainberg, director of an AIDS centre with McGill University and the Jewish General Hospital, who was not involved with the studies.

“This is really good news, it’s a step in the right direction, but we would’ve hoped for better.”

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More than half of the world’s 37 million people currently living with HIV are women, with the majority residing in sub-Saharan Africa, which has some of the world’s highest infection rates.

For the past decade, the non-profit International Partnership for Microbicides (IPM) has been developing a vaginal ring that can protect at-risk women from HIV infection. Similar to vaginal rings used as contraceptives, the device releases an anti-HIV drug called dapivirine, which prevents the virus from replicating.

The vaginal ring has excited researchers because it offers invisible protection — a huge benefit to women who are vulnerable to rape or lack control over their sexual reproductive health.

Better yet, it only needs replacing once a month, offering a lower-maintenance option than alternative HIV prevention methods, like prophylactic pills or microbicidal gels. Both of which require daily or sex-dependent use and have shown low adherence among African women, meaning users have struggled to follow the products’ requirements.

Two large clinical trials of the vaginal ring began in 2012, with 4,588 women enrolled across sites in Uganda, South Africa, Malawi and Zimbabwe.

In both studies, the vaginal ring was the most protective for adult women. In one study — dubbed ASPIRE and led by the U.S. National Institutes of Health — the HIV infection rate was reduced by 61 per cent for women over 25 and 56 per cent for those over 21. These results were published Monday in the New England Journal of Medicine.

The other, called the Ring Study, is led by IPM and saw reductions by 37 per cent for women over 21.

“The ring is the first long-acting HIV prevention method designed specifically for women (and) two large studies have confirmed the ring’s efficacy with statistical significance,” said IPM’s chief medical officer, Dr. Annalene Nel, who is leading the Ring Study. “Today’s results give us hope that we must and can do better.”

But in both studies, the vaginal ring showed little to no protection for women under the age of 21. In the Ring Study, the vaginal ring reduced infections by only 15 per cent for women between 18 and 21; in ASPIRE, the added protection for these women was zero.

“I think we know from lots of settings — from HIV treatment, from contraception — that women who are younger often have problems with adherence,” said Dr. Jared Baeten, a University of Washington professor with the ASPIRE team.

He added that more work is needed to unpack why the vaginal ring performed poorly in younger women.

Nonetheless, the researchers believe their findings are promising enough to stop giving placebos to women in the South African control group of the Ring Study (the ASPIRE study has already ended), and start giving them the microbicidal versions.

The IPM also hopes to license the vaginal ring by 2017 and is exploring development of a different version that doubles as a contraceptive. There are also plans to produce a vaginal ring that can last for three months instead of one.

For Paula Donovan, co-director of the international advocacy organization AIDS-Free World, she considers Monday’s trial results to be a “completely good news story,” though she emphasized that she is not a scientist.

She considers the vaginal ring a promising intermediate step and the “beginning of what everybody’s hoping will be the perfect prevention method.”

“There’s just been nothing to date that’s held out any hope for women of reproductive age who don’t necessarily have autonomy over their sexual lives,” Donovan said. “To have something like this, that can be used by women with or without the knowledge of their sexual partners … that’s just incredibly welcome.”

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